A COMPUTER-PROGRAM TO ANALYZE MULTIPLE-SEASON CROP MODEL OUTPUTS

Management-oriented simulation models of the growth, development, and yield of annual crops are useful tools for screening management option s on the computer. Until recently, a limitation of these models has be en the inability to simulate more than one cropping season at a time. The capability to simulate long-term field experiments with such model s now exists, in which the simulated soil water, N, organic C, and cro p residue outputs from one model run become the input conditions for t he next, Simulations of crop rotations can produce large quantities of data, especially if the simulation experiment involves replications a cross different years. Computer software was written to perform simple analyses of such simulation experiments. The major purpose of the sof tware is to allow the user to investigate the stability and profitabil ity of crop sequences, The program calculates summary statistics for m odel output variables; these are presented to the user in tabular and graphical forms. Net monetary returns or gross margins can also be cal culated, and price and cost variability can be taken into account in t he analysis. The program allows rapid, preliminary analysis of a parti cular crop sequence from replicated simulation experiments and can hel p the user to assess whether the sequence warrants further evaluation. The program can also be used to summarize the results from historical long-term field trials. The analyses performed constitute a first ste p in investigating the sustainability of a particular cropping sequenc e for a specified length of time.